1. Technical Field
The present invention relates to a thermal detector, a thermal detection device, an electronic instrument, and a thermal detector manufacturing method.
2. Related Art
Thermal detection devices are known as light sensors. Thermal detectors absorb light that has been emitted from an object in a light-absorbing layer, convert the light to heat, and measure the change in temperature with a heat-detecting element. Thermal detectors include thermopiles that directly detect the increase in temperature accompanying light absorption, pyroelectric-type elements that detect a change in electrical polarity, and bolometers that detect the increase in temperature as a change in resistance. Thermal detectors have a characteristically wide wavelength range over which measurements can be made. In recent years, semiconductor fabrication technologies (e.g., MEMS technologies) have been used, and the production of smaller-scale thermal detectors has been attempted.
In order to enhance the detection accuracy and improve the responsiveness of a thermal detector, it is important to generate heat in the light-absorbing layer in an efficient manner, and to transmit the heat generated in the light-absorbing layer to the heat-detecting element in an efficient manner.
An example of a structure of a pyroelectric-type infrared sensor is described in, e.g., Japanese Laid-Open Patent Application Publication No. 2004-279103. In the example described in this publication, an insulating film for carrying a pyroelectric element is formed on a cavity, and a pyroelectric element is formed on the insulating film. The pyroelectric element has a structure in which a pyroelectric material is sandwiched between upper and lower electrodes.
An example in which an optical resonator is configured in an infrared sensor is described in, e.g., Japanese Laid-Open Patent Application Publication No. 2010-127891. In the example described in this publication, in a bolometer-type infrared sensor, the distance between a reflective film and a heat-sensitive film is set to an integer multiple of λ/4 (where λ is the wavelength of light), thereby causing resonation of light and enhancing the efficiency of light absorption by the heat-sensitive film.